Monday, January 21, 2013


Metal/Nonmetal Health Inspection Procedures Handbook PH06-IV-1(1)

October 2006 10-1

Chapter 10


I. Introduction

This chapter includes sampling procedures for evaluating four types of ionizing radiation


: alpha, beta, gamma, and x-ray. Ionizing radiation can cause cancer. At high

doses, ionizing radiation causes radiation sickness. Ionizing radiation can be emitted by

the mined ore, the surrounding rock, or nuclear gauges such as those that monitor the

flow of materials. Miners can be exposed to hazardous levels of ionizing radiation at

mines other than those producing radioactive minerals.

II. Definitions

Alpha Counter/Scaler

- an instrument that counts alpha decay events when used with a

scintillation detector.

Alpha Radiation

- a particle that has a positive (+2) charge and is emitted from the

nucleus of an atom. An alpha particle consists of two protons and two neutrons. When

inhaled, dust containing alpha producing particles can cause lung cancer. While alpha

particles travel at a high energy rate, they are so large that a sheet of paper or a few

centimeters of air can block their path. Alpha particles are emitted by radon, uranium,

and thoron. Examples of alpha emitters are uranium-238, radium-226, and radon-222.

Beta Radiation

- a particle that has a negative (-1) charge and is emitted from the

electron shell of an atom. A beta particle consists of one electron. Beta radiation has

more penetrating capability than alpha radiation because the particle is much smaller.

Even so, a light-weight barrier material, such as cardboard or sheet metal, can block beta


Gamma Radiation

- short wavelength electromagnetic radiation emitted from

radioactive elements such as uranium. Lead or concrete can block this type of radiation.

Geiger-Mueller counter

- small hand-held meter designed to measure x-ray and gamma



- the time required for a radioactive substance to lose 50 % of its activity by

decay. Each radionuclide has a characteristic half-life.

Ionizing Radiation

- a form of energy capable of changing a stable, electrically-neutral

atom into an unstable electrically-charged particle (ion). Radiation from uranium, radon,

and other radioactive sources is ionizing.

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- a form of an element that differs from other forms of the same element in the

number of neutrons in each atom’s nucleus. Isotopes of the same element may have

different levels of stability and potential radioactivity.

Kusnetz method -

a method for determining exposure to alpha radiation emitted from

radon and thoron daughters/progeny. It was developed in the 1950's by H. L. Kusnetz.

Radioactive decay

- the natural process of a radioactive material shedding mass from its

nucleus. After each decay event, another element or isotope of lesser mass is formed.

The decay process trends toward more stable elements with elemental lead (Pb 207) the

most stable.


- the radioactive gas produced by the radioactive decay of the element radium.

Radon Daughters/Radon Progeny

- unstable, short-lived decay products of radon gas

which emit alpha particles during the decay process. (Terms are used interchangeably.)


- abbreviation of Roentgen Equivalent Man - a unit for measuring the absorbed

dose by humans (and biological effects) of ionizing radiation. Personal exposure limits

for gamma and X-Ray radiation are expressed in REMs.

Roentgen (R)

- a unit for measuring X-rays or gamma rays. For radiation protection, one

R equals the dose measurement of one REM.

Scintillation detector

- type of detector used to determine alpha emissions from filter

samples. Operates as photons are released from a zinc sulfide phosphor and amplified

with a photo-multiplier tube. Works in train with an alpha scaler/counter.


- a gas formed from the radioactive decay of thorium (Th), an element. Thoron

is similar to radon as a health hazard in that respirable thoron daughters/progeny emit

alpha radiation. It is an isotope of radon gas.

Working level (WL)

- the unit of measurement of airborne radon or thoron alpha

particles in an area. Working levels are used to express the concentrations of radon

daughters in underground mines for compliance sampling. It is calculated by the

general formula:

WL = Radiation Level X Time (hours)

Metal/Nonmetal Health Inspection Procedures Handbook PH06-IV-1(1)

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Working level months (WLM)

- the unit of measurement for determining compliance

with the annual exposure limit for miners. A lung dose of 10 REM is equal to 1.0 WLM.

For compliance determination, 30 CFR § 57.5040 requires WLM be calculated by the

following formula:

WLM = Number of hours exposed in a month X average WL

173 hours per month

X-ray radiation

- is similar to gamma radiation in that it is a ray and not a particle but

different in that it is man-made versus naturally-occurring radiation. X-rays are produced

when a focused electron beam is aimed at a Tungsten surface resulting in an emanation of

high energy, highly penetrating radiation. Lead or thick concrete can block this type of


III. Standards Applicable to Ionizing Radiation

A. Exposure Limits

Title 30 CFR §§ 57.5037 through 57.5047 contain the ionizing radiation exposure

limits for miners:


Miners shall not be exposed to air having a radon daughter concentration

exceeding 1.0 working level (WL) in active workings.


Ventilation is the primary means for controlling radon daughters to below

the allowable exposure limits. However, respirators approved by NIOSH

for radon daughters shall be used in atmospheres whose radon daughter

concentrations exceed 1.0 WL.


If the WL concentration exceeds 10 WL, protection against radon gas

shall be provided by supplied air devices or by face masks containing

absorbent material capable of removing both radon and its daughters.


No miner shall be exposed to more than 4.0 WLM in any calendar year.


Annual individual gamma radiation exposure shall not exceed 5 REMs.

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B. Sampling requirements

1. Underground Non-Uranium Mines

a. Screening Frequency

- Annually sample all metal and nonmetal

mines where radon daughters have exceeded 0.1 WL in the past,

per 30 CFR § 57.5037(a). Sample remaining nonmetal and stone

mines every three years. Sample new or reopened mines as soon

as possible. Sample exhausts (return airways) and poorly

ventilated areas for radon daughters. Where any screening sample

exceeds 0.1 WL, follow the additional procedures below.

b. Concentration 0.1 WL

- Sample all active work areas four times

annually (Full-Time Permanent - FTP) or whenever conducting a

regular inspection (Intermittent - INT). Also evaluate the mine

operator's (quarterly) sampling procedures for possible


Monitor mine operator compliance with 30 CFR §§ 57.5037(a)(2),

57.5038, 57.5039, 57.5040(a)(2), 57.5041, 57.5044, 57.5045, and

57.5046 where radon/thoron daughters concentrations exceed 0.3


Check the mine operator's sampling records and thoroughly sample

any work area exceeding 0.3 WL. A mine operator may invoke the

five consecutive week provisions of 30 CFR §§ 57.5037 and

57.5040. If MSHA sampling verifies the mine operator's claims

that alpha emissions have remained under 0.3 WL, the operator

can suspend weekly sampling in favor of quarterly sampling.

However, the mine operator must continue weekly sampling and

worker exposure record keeping if MSHA results exceed 0.3 WL.

2. Underground Uranium Mines

a. Sampling Frequency

- Sample all active work areas for both

radon and thoron daughters four times annually or whenever a

regular inspection is conducted. Also, monitor compliance with

30 CFR §§ 57.5037 and 57.5040. Where any sample exceeds 0.1

WL, follow the additional procedures below:

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October 2006 10-5

b. Concentration 0.1 WL

- Evaluate the mine operator's sampling

procedures and employee exposure records to verify conformity to

the standard.

Monitor mine operator compliance with 30 CFR §§ 57.5037,

57.5038, 57.5039, 57.5041, 57.5044, 57.5045 and 57.5046 where

radon daughters concentrations exceed 0.3 WL.

Check the mine operator's sampling records and thoroughly sample

the area in question if an operator invokes the five consecutive

week provisions of 30 CFR §§ 57.5037 and 57.5040. If MSHA

sampling verifies the operator's findings, the mine operator can

revert to biweekly sampling. If MSHA sampling results exceed

0.3 WL, however, the operator must continue weekly sampling.

c. Screening for Gamma Radiation

- Perform annual gamma

radiation screening in all underground mines where radioactive

ores are mined. Monitor compliance with 30 CFR § 57.5047.

• Average readings in excess of 2 milliroentgens per hour

(mR/hr) require implementation of personal dosimeters for

all persons affected. Note: 2 milliroentgens per hour is

equivalent to 2 millirems per hour.

• Perform calculation presented in Appendix to obtain

projected shift exposure. Multiply projected shift exposure

by the number of shifts per week if doing a one day

screening and divide by 1000 to obtain estimated REM

value for a work week. Compare this calculation with

records to check the consistency of recorded exposures

with calculated exposures. Any significant discrepancy

should be investigated.

• Records of cumulative individual exposures should be

checked to ensure compliance with 5 REM annual

exposure limit.

• Failure to provide personal dosimeters and keep records of

cumulative individual exposures are citable offenses when

circumstances require, (see item 1 above.)

Sampling Uranium Mines

1. For radon samples, select locations that are most representative of the

miner’s average exposure.

2. When in doubt, sample all prominent work stations, giving priority to the

face and out of the way work areas
. Take representative samples in all

active stoping areas, travelways, shops, lunch rooms, and other occupied

mine areas.

C. Guidelines for Enforcement Sampling For Alpha Radiation

1. Follow the sampling strategies outlined in paragraphs A. and B. above.

2. Check air currents at the sampling locations for unusual conditions, using

a smoke-cloud producing apparatus and/or anemometer.

3. Measure and record the ventilation quantity at the time and place of


4. Take ample notes regarding all conditions which might affect radon

daughter concentrations in the areas sampled.

5. Follow good sampling procedures.

6. Take all possible precautions to maintain the integrity of the calibration

sampling equipment.

7. Take as many samples as necessary to determine compliance with the

applicable standard and to establish an appropriate time limit for the

abatement of any citations which are issued.

D. Collecting the Sample

1. Pump and Filter Sampling Combination Kusnetz Method

a. Calibrate sampling pump at 2.0 Lpm or more (up to the stable limit

of your personal sampling pump), using the procedures in Chapter

4, and calibrate the readout instrument.